Display case



Dec. 6, 1966 J. H. BRENNAN ETAL 3,

DISPLAY CASE Filed Aug. 6, 1965 o 8 O,/52 K o 44 1 W 4 42 3 48 I6 H T IO++++++O sag/7* I N VENTOR.

JAMES H. BRENNAN B MALCOLM D MACMASTER JM w/M A T TORNE Y 3,289,432DISPLAY CASE James H. Brennan, Trenton, NJ., and Malcolm l).

Mac-Master, Yardley, Pa., assignors to Emhart Corporation, Bloomfield,Conn., a corporation of Connecticut Filed Aug. 6, 1965, Ser. No. 477,6815 Claims. (Cl. 62-256) This invention relates to refrigerated displaycases of the type wherein there is a storage space having an accessopening, and an air curtain embodying a plurality of layers of air isdirected across the access opening to shield the storage space fromambient air.

Constructions of this type are widely used and generally are arranged sothat the innermost layer of air in the air curtain is refrigerated andmaintained at a lower temperature than the outermost layer of airadjacent the ambient air. Nevertheless, as the display case is used,moisture penetrates the air curtain as persons reach into the storagespace and disturb the air curtain and additional moisture tends tomigrate or be drawn into the air curtain by entrainment from the ambientair. Thereafter as the air used in producing the air curtain isrecirculated and passed through ducts or passages and an evaporator torefrigerate the same, the moisture deposits on the coils, fins andsurfaces of the evaporator and air ducts. As a result, snow, frost orice which builds up progressively on such surfaces not only reduces theheat transfer from the air to the evaporator but seriously restricts thepassages and reduces the velocity of the air flowing through the ductsand forming the air curtain. The temperature of the air in the aircurtain and the migration or penetration of moisture into the aircurtain is then increased so that the accumulation of ice, frost andsnow on the refrigerated coils and surfaces is increased and thedevelopment of undesired conditions are progressively accelerated. Thissituation is particularly aggrevated when the display case is operatedat low temperatures, as when frozen foods, ice cream and the like are ondisplay; since the humidity of the refrigerated air is then very low,the migration of moisture into the air curtain is increased, and thedeposition of moisture on the coils and fins takes place rapidly and inlocalized areas where it first contacts low temperature surfaces.Defrosting of the evaporator must then take place frequently and thetemperature of the air in the air curtain and storage space fluctuatesconsiderably.

In accordance with the present invention, these objections andlimitations of prior refrigerated display cases utilizing an air curtainare reduced or overcome and a simplified construction provided whichserves to operate automatically to compensate for variations in the aircurtain resulting from accumulation of snow, ice or frost on theevaporator and surfaces used for reducing the temperature of the air inthe air curtain.

These results are preferably attained by constructing and arranging theducts through which the air forming the air curtain is passed with acommon passage or plenum chamber to which the moisture containing returnair from the air curtain is directed and by providing a condenserby-pass for the air utilized in producing the outer or protective layerof air in the air curtain. In this way, less return air is caused topass over the condenser when the evaporator and its surfaces becomerestricted by accumulations of frost or snow thereon, whereas thevelocity of the air in the outer protective layer of the air curtain isincreased and the protective action thereof is rendered more effective.

Accordingly, the principal objects of the present invention are toimprove the operation and simplify-the construction of refrigerateddisplay cases utilizing an air curtain to shield a storage space thereinfrom ambient United States Patent 0 air; to automatically vary theaction of the elements employed in producing an air curtain embodyingmultiple layers of air; to adjust the amount and velocity of aircirculated through ducts or passages to produce a multi layer aircurtain in response to the accumulation of snow, frost or ice onsurfaces over which such air is passed; and to decrease the frequencyand duration of the defrosting cycle required to assure proper operationof display cases.

A specific object of the present invention is to provide a refrigerateddisplay case utilizing a multi-layer air curtain with means forautomatically causing the air used in producing an outer protectivelayer of air, to by-pass the evaporator and to vary the amount of airthus by-passed as the accumulation of frost, snow and ice on thesurfaces of the evaporator increases.

These and other objects and features of the present invention willappear from the following description thereof wherein reference is madeto the figures of the accompanying drawing.

The drawing is a vertical sectional view of a typical form ofrefrigerated display case embodying the present invention.

In that form of the invention chosen for purposes of illustration in thedrawing, the display case has an insulated base 2, an insulated rearwall 4, an insulated top 6 extending forwardly from the rear wall 4 andan insulated front wall 8 extending upward from the base 2. The upperedge 10 of the front wall 8 is spaced from the top 6 of the case toprovide an access opening 12 in the front of the case through whichpersons may reach into the storage space 14 to place articles in orremove articles from the storage space and shelves 16 therein.

In order to shield the storage space from ambient air, an air curtain 18is established for directing air across the access opening 12. The aircurtain comprises at least two parallel layers of air which flow in thesame direction and, as shown, includes an inner layer of refrigeratedair 20 which is directly downwardly across the access opening from anoutlet or nozzle 22, and an outer or protective layer of air 24 which isdirected downwardly adjacent to the inner layer 20 from an air outlet ornozzle 26.

Both, or all, of the layers of air embodied in the air curtain 18 arerecirculated in establishing and maintaining the air curtain. For thispurpose, the case is provided with a return air passage 28 locatedadjacent the inner side of the lower front Wall 8 of the case and has anair inlet opening 30 positioned near the upper edge 10 of the front wallto receive air from the air curtain. The lower end of the return airpassage 28 communicated with a plenum chamber 32 located above theinsulated base 2 of the case and beneath the bottom 34- of the storagechamber 14. An evaporator section or drying coil 36 is located in theplenum chamber and the layers of air from the air curtain are drawndownward into the return air passage 28 and into the plenum chamber 32so as to pass over the coil 36 by means of a blower or fan 38. In thisway, the return air from the air curtain is caused to flow through acommon return passage and the common plenum chamber where they maymingle and give up moisture which has penetrated or been entrained byeither, both or all of the layers of air embodied in the air curtain.While the coil 36 preferably is refrigerated to a sufiicient extent tocool the air passing thereover and cause moisture to condense on tubesand fins of the coil without causing the moisture to freeze or toproduce a build-up of snow, frost or ice thereon, the moisture thuscondensed may drip from the coil to a drain outlet 40 Whereas the airpassing to the blower and returning to maintain the air curtain isrelatively dry.

The air from the blower 38 is directed to and through two separate ductsor passages which, as shown, extend vertically between the rear wall 4of the case and the back wall 42 of the storage space 14, and forwardlybeneath the top 6 of the case to the air outlets or nozzles 22 and 26 atthe upper edge of the access opening 12. For this purpose, a metal orother thermally conducting divider 44 is provided which cooperates withthe rear wall 4 and top 6 to form a protective air duct 46. At the sametime, the divider 44 cooperates with the back wall 42 of the storagechamber to form a refrigerated air duct 48. Two or more evaporators orevaporator sections 50 and 52 are located in the refrigerated air duct48 and air discharge openings 54 may be formed in the back wall 42 topermit refrigerated air from the duct 48 to flow forward into thestorage space 14 and beneath or over the shelves 16 therein. On theother hand, the protective air duct 46 is preferably free andunobstructed throughout its length although the air passing therethroughis cooled or refrigerated to some extent by heat exchange from theevaporators and refrigerated air in the duct 48 through the thermallyconducting divider 44.

The lower inlet opening 56 of the protective air duct 46 and the lowerinlet opening 58 of the refrigerated air duct 48 are both located beyondthe drying coil 36 and blower 38 and communicate with the common plenumchamber 32 so that both ducts are supplied with return air from the aircurtain under the same pressure and conditions of temperature andhumidity. Thereafter, the air which is to form the outer protectivelayer of air 24 in the air curtain 18 flows freely through theprotective air duct 46 to the outlet opening 26 so as to be directeddownwardly across the access opening 12 toward the inlet opening 30 ofthe return air passage 28. In a similar way, the air which is to formthe inner refrigerated layer or layers of air 20 of the air curtain 18is caused to flow upward through the refrigerated air duct 48 and overthe refrigerating coils 50 and 52 to the inner air outlet or nozzle 22.From the air outlet 22, the refrigerated layer of air 20 is directeddownwardly across the access opening 12 between the protective layer ofair 24 and the storage space 14 to the return air inlet 30 at the upperend of the return air passage 28.

' With this construction, the amount of air and the velocity of flowthereof through the protective and refrigerated air ducts 46 and 48 willdepend primarily upon the cross sectional area of the ducts and theirinlet openings 56 and 58 respectively and the amount of obstruction orrestriction to air flow imposed by the coils and fins of the evaporators50 and 52 in the refrigerated air duct 48, as well as the size or powerof the blower 32. Since these elements are fixed or may be establishedby the design and construction of the case and by control of the blower32, the amount and velocity of the air discharged from the air outletsor nozzles 22 and 26 and forming the layers of air which make up the aircurtain 18 can be predetermined to assure the desired operation of thecase.

Thereafter, as operation continues, the air flowing through therefrigerated air duct 48 and over the evaporators 50 and 52 will bematerially reduced in temperature so as to deposit additional moisturein the form of snow, frost or ice on the coils and fins of theevaporators and, in some instances, on the walls or other surfaces ofthe refrigerated air duct 48. However, little if any such accumulationswill take place within the protective air duct 46. As a result, therestriction to flow of air through the refrigerated air duct willincrease as the frost accumulations build up, and such accumulations andrestriction will take place more rapidly as the humidity of the ambientair and the migration and entrainment of moisture in the returned andrecirculated air from the air curtain increases.

The amount and velocity of the air flowing through the ducts 46 and 48and forming the layers of air 28 and 24 of the air curtain 18 willtherefore be automatically and progressively proportioned or varied asthe resistance to flow of air through the refrigerated air duct 48 isvaried. Moreover, as the velocity of the air flowing through therefrigerated air duct 48 decreases, its tem perature will be reducedwhile the velocity of the protective air flowing through duct 46 willincrease and its temperature will be decreased to a lesser degree.Nevertheless, the higher velocity of the protective layer of air 24resulting from such conditions serves to increase the protective actionthereof by decreasing the possibility of heat exchange therethroughbetween the ambient air and the refrigerated air in the storage spaceand forming the. inner layer 20 of the air curtain.

The same increased protective effect of the outer layer of protectiveair at increased velocity is attained upon increase in the humidity ofthe ambient air. At such times, the tendency for frost and snow to buildup on the evaporators 50 and 52 increases upon an increase in humidityof the ambient air, whereby the protective effect of the unrestrictedair flow through the duct 46 and in the outer layer of air 24 of the aircurtain is increased.

In this way, an automatic and progressive variation in the operation ofthe display case is effected without resort to the use of mechanicalelements or control means. As a result, the frequency of the defrostingcycles required for removing excessive frost, snow and ice from theevaporators 50 and 52 is decreased and the length of the refrigeratingcycles increased. The refrigeration efficiency of the display case isthereby increased whereas the construction and operation thereof issimplified.

While the construction shown in the drawing and described above isdesigned to establish an air curtain embodying only two layers of air,the nozzles or outlet openings and the ducts provided for supplying airthereto may be increased in number as desired to provide an air curtainembodying any desired number of layers of air progressing in temperaturefrom the refrigerated storage space outward to the ambient air.Furthermore, it is not always necessary or desirable to provide a dryingor humidifying coil in the plenum chamber particularly when the case wilbe employed in locations wherein the humidity is relatively low.

The present invention further may be used in combination with elementsdesigned to recover any recirculate spill air and/ or to vent excessrecirculated air from the protective air circuit as disclosed incopending application Serial No. 477,730, filed Aug. 6, 1965.

It will thus be apparent that numerous changes in the form,construction, arrangement and combination of the elements employed inthe practice of the present invention may be made. In view thereof, itshould be understood that the particular embodiment of the inventionshown in the drawing and described above is intended to be illustrativeonly and is not intended to limit the scope of the invention.

We claim:

1. A refrigerated display case having a storage space therein providedwith an access opening in the front thereof and means for establishingan air curtain embodying a plurality of layers of air directed acrosssaid access opening between said storage space and ambient air, saidmeans comprising an inner refrigerated air duct provided with an outletopening located on one side of the access opening for directing arefrigerated layer of air across said access opening as one layer ofsaid air curtain, an outer protective air duct provided with an outletopening located adjacent said one side of the access opening and fartherfrom said storage space than the outlet opening of the refrigerated airduct for producing an outer protective layer of air as a second layer ofsaid air curtain, air inlet means located at the opposite side of saidaccess opening in position to receive air from both said layers of airin the air curtain, a plenum chamber communicating with said air inletmeans, said inner refrigerated air duct and said outer protective airduct each communicating with said plenum chamber to receive airtherefrom, blower means operable to circulate air from said air inletmeans through said plenum chamber and both said inner refrigerated airduct and said outer protective air duct to their respective outletopenings, and an evaporator located in at least said refrigerated airduct and beyond said plenum chamber to refrigerate air passing throughthe refrigerated air duct, the cross sectional area of said refrigeratedair duct and said protective air duct through which air flows to theirrespective outlet openings during operation of said display case beingvariable in response to accumulation of frost on the surfaces of saidducts and any refrigerating means therein, whereby the proportion of theair from said plenum chamber which flows through said refrigerated airduct and protective air duct to form the inner refrigerated layer of airand the outer protective layer of air in said air curtain will bevariable and dependent in part at least upon the amount of frostaccumulated on the surfaces and refrigerating means in said refrigeratedand protective air ducts, respectively.

2. A refrigerated display case as defined in claim 1 wherein theprotective air duct is located in heat exchanging relation with saidrefrigerated air duct.

3. A refrigerated display case as defined in claim 1 wherein a dryingcoil is located in said plenum chamber to decrease the humidity of airpassing therethrough to said refrigerated and protective air ducts.

4. A refrigerated display case as defined in claim 1 wherein said plenumchamber is located below said storage space and the refrigerated airduct and protective air ducts extend vertically at the rear of thestorage space and forwardly to outlet openings positioned adjacent theupper side of the access opening at the front of the case and the inletopening for the common return air duct is located near the lower side ofthe access opening.

5. A refrigerated display case as defined in claim 1 wherein thevelocity of the air forced through the outlet openings of saidrefrigerated air duct and said protective air duct and forming saidlayers of air in said air curtain is variable in response to theresistance to air flow through the refrigerated air duct resulting fromaccumulation of frozen moisture on said evaporator.

References tlited by the Examiner UNlTED STATES PATENTS 3,063,25211/1962 Lamb 62-256 3,063,253 11/1962 Dickson 62-256 3,063,254 11/1962Dickson 62256 3,186,185 6/1965 Bently 62255 WILLIAM J. WYE, PrimaryExaminer.

1. A REFRIGERATED DISPLAY CASE HAVING A STORAGE SPACE THEREIN PROVIDEDWITH AN ACCESS OPENING IN THE FRONT THEREOF AND MEANS FOR ESTABLISHINGAN AIR CURTAIN EMBODYING A PLURALITY OF LAYERS OF AIR DIRECTED ACROSSSAID ACCESS OPENING BETWEEN SAID STORAGE SPACE AND AMBIENT AIR, SAIDMEANS COMPRISING AN INNER REFRIGERATED AIR DUCT PROVIDED WITH AN OUTLETOPENING LOCATED ON ONE SIDE OF THE ACCESS OPENING FOR DIRECTING AREFRIGERATED LAYER OF AIR ACROSS SAID ACCESS OPENING AS ONE LAYER OFSAID AIR CURTAIN, AN OUTER PROTECTIVE AIR DUCT PROVIDED WITH AN OUTLETOPENING LOCATED ADJACENT SAID ONE SIDE OF THE ACCESS OPENING AND FARTHERFROM SAID STORAGE SPACE THAN THE OUTLET OPENING OF THE REFRIGERATED AIRDUCT FOR PRODUCING AN OUTER PROTECTIVE LAYER OF AIR AS A SECOND LAYER OFSAID AIR CURTAIN, AIR INLET MEANS LOCATED AT THE OPPOSITE SIDE OF SAIDACCESS OPENING IN POSITION TO RECEIVE AIR FROM BOTH SAID LAYERS OF AIRIN THE AIR CURTAIN, A PLENUM CHAMBER COMMUNICATING WITH SAID AIR INLETMEANS, SAID INNER REFRIGERATED AIR DUCT AND SAID OUTER PROTECTIVE AIRDUCT EACH COMMUNICATING WITH SAID PLENUM CHAMBER TO RECEIVE AIRTHEREFROM, BLOWER MEANS OPERABLE TO CIRCULATE AIR FROM SAID AIR INLETMEANS THROUGH SAID PLENUM CHAMBER AND BOTH SAID INNER REFRIGERATED AIRDUCT AND SAID OUTER PROTECTIVE AIR DUCT TO THEIR RESPECTIVE OUTLETOPENINGS, AND AN EVAPORATOR LOCATED IN AT LEAST SAID REFRIGERATED AIRDUCT AND BEYOND SAID PLENUM CHAMBER TO REFRIGERATE AIR PASSING THROUGHTHE REFRIGERATED AIR DUCT, THE CROSS SECTIONAL AREA OF SAID REFRIGERATEDAIR DUCT AND SAID PROTECTIVE AIR DUCT THROUGH WHICH AIR FLOWS TO THEIRRESPECTIVE OUTLET OPENINGS DURING OPERATION OF SAID DISPLAY CASE BEINGVARIABLE IN RESPONSE TO ACCUMULATION OF FROST ON THE SURFACES OF SAIDDUCTS AND ANY REFRIGERATING MEANS THEREIN, WHEREBY THE PROPORTION OF THEAIR FROM SAID PLENUM CHAMBER WHICH FLOWS THROUGH SAID REFRIGERATED AIRDUCT AND PROTECTIVE AIR DUCT TO FORM THE INNER REFRIGERATED LAYER OF AIRAND THE OUTER PROTECTIVE LAYER OF AIR IN SAID AIR CURTAIN WILL BEVARIABLE AND DEPENDENT IN PART AT LEAST UPON THE AMOUNT OF FROSTACCUMULATED ON THE SURFACES AND REFRIGERATING MEANS IN SAID REFRIGERATEDAND PROTECTIVE AIR DUCTS, RESPECTIVELY.